Polymer nanoparticles have attracted increased attention over the past several years in a variety of fields including catalysis, combinatorial chemistry, protein supports, magnets, and photonic crystals. Nanoparticles have been used in rubber compositions to improve physical properties of rubber moldability and tenacity. In some instances the inclusion of polymer compositions with certain functional groups or heteroatomic monomers can produce beneficial and unexpected improvements in rubber compositions.
Charged nanoparticles may have a number of possible applications, such as in electronic devices, or in rubber or other polymer matrices. In some electronic display applications, such as QR-LPD, charged particles may be used to present a pictorial or textual display. It is a challenge, however, to provide particles that have a durable constitution and a stable charge. It is also a challenge to produce durable nanoparticles that are very hard and have highly spherical surfaces.
Herein, a method is provided for making nanoparticles, including the steps of: combining a hydrocarbon solvent and an aprotic, polar co-solvent, a mono-vinyl aromatic monomer, polymerization initiator, a solution stabilizer, and a first charge of a cross-linking agent. Subsequently, a second charge of cross-linking agent is added. The nanoparticles have an average diameter of 5 nanometers to about 10,000 nanometers.
Furthermore, spherical cross-linked nanoparticles are also provided. The spherical nanoparticles have a core formed from a polymeric seed that includes a mono-vinyl aromatic core species cross-linked with a cross-linking agent. The core has an average diameter of 5 nanometers to 10,000 nanometers. The mono-vinyl aromatic core species comprises polymeric chains radiating from a center of the core. Furthermore, the nanoparticles meet the following equation:0.90≦(D1/D2)≦1.1wherein D1 is a first diameter of a nanoparticle and D2 is a second diameter of the nanoparticle, and D1 and D2 intersect at right angles.
Furthermore, spherical cross-linked nanoparticles are also provided. The spherical nanoparticles have a core formed from a polymeric seed that includes a mono-vinyl aromatic core species cross-linked with a cross-linking agent. The core has an average diameter of 5 nanometers to 10,000 nanometers, and the cross-linking agent comprises 30% to 60% by weight of the combined weight of the mono-vinyl aromatic species and the cross-linking agent. The mono-vinyl aromatic core species comprises polymeric chains radiating from a center of the core. Furthermore, the nanoparticles meet the following equation:0.90≦(D1/D2)≦1.1wherein D1 is a first diameter of a nanoparticle and D2 is a second diameter of the nanoparticle, and D1 and D2 intersect at right angles.
Herein throughout, unless specifically stated otherwise: “vinyl-substituted aromatic hydrocarbon” and “alkenylbenzene” are used interchangeably. Furthermore, the terms “a” and “the,” as used herein, mean “one or more.”